Documentation page Viewing your repository's releases and tags - GitHub Docs reads:
To the right of the list of files, click Releases
but repositories like GitHub - numba/numba: NumPy aware dynamic Python compiler using LLVM and many others don’t have Releases tag/button:
Is this a Github issue or developers are responsible for configuring this page?
Yes, repository admins can configure if the “releases” section should appear. Interestingly I see it when I visit that repository. 
And the section appears to be present: The “Version 0.55.1” part is what appears right under the “Releases” heading. I wonder if you have a browser add-on or anything else that might mess with website elements?
I see Releases in the toolbar above the list of files, not to the right of it:
I’m using Google Chrome Version 100.0.4896.88 (Official Build) (64-bit). The page renders the same way with AdblockPlus disabled.
Yes, I have a few extensions installed, including Refined GitHub v22.4.21 (GitHub - refined-github/refined-github: Browser extension that simplifies the GitHub interface and adds useful features). When I disable it, the page renders the same way as on your screenshot. I just discovered that.
@pauljurczak and @jdevstatic you can click on the latest release that shows ( in your case version 0.55.1) and it will automatically redirect to the releases page.
